The present invention relates generally to disk drives for storing data. More specifically, the present invention relates to an E-block having one or more actuator arms which include one or more integrally formed weighted segments to improve the resonance characteristics and the fragility of the E-block.
Disk drives are widely used in computers and data processing systems for storing information in digital form. These disk drives commonly use one or more rotating storage disks to store data in digital form. Each storage disk typically includes a data storage surface on each side of the storage disk. These storage surfaces are divided into a plurality of narrow, annular, regions of different radii, commonly referred to as xe2x80x9ctracksxe2x80x9d. Typically, an E-block having one or more actuator arms is used to position a data transducer of a transducer assembly proximate each data storage surface of each storage disk. The E-block is moved relative to the storage disks with an actuator motor. Depending upon the design of the disk drive, each actuator arm can retain none or two transducer assemblies.
The accurate and stable positioning of each transducer assembly near each data storage surface is critical to the transfer and retrieval of information from the disks. As a result thereof, vibration in the E-block and the transducer assembly can cause errors in data transfers due to inaccuracies in the positioning of the data transducers relative to the storage disks. This is commonly referred to as xe2x80x9coff-track motionxe2x80x9d. Additionally, extreme shock loads during shipping, handling, and/or installation of the disk drive can cause extreme vibration in the E-block and the transducer assemblies. The extreme vibration can cause the data transducers to overcome the suspension load force and leave the disk surface, resulting in a xe2x80x9cslapxe2x80x9d or xe2x80x9ccrashxe2x80x9d when returning to the storage disk surface.
Because it is most economical to utilize all surfaces of the disks in a disk drive, the E-block which has the heads attached at the ends of each of its arms results in an asymmetry of the top and bottom arms with respect to the inner arms. The outer actuator arms retaining only one head are referred to as being xe2x80x9cdepopulatedxe2x80x9d. The inner actuator arms retaining two transducer assemblies are referred to as being xe2x80x9cpopulatedxe2x80x9d. The depopulated actuator arms bend and flex at different frequencies than the populated actuator arms as a result of the asymmetrical nature of having only one transducer assembly coupled to the actuator arm. The result of this asymmetry is additional vibration modes and xe2x80x9coff trackxe2x80x9d motion.
FIG. 1A is a top plan view which illustrates the vibration in a prior art E-block 10P and transducer assemblies 12P with force applied by an actuator motor (not shown). FIG. 1B is a side perspective view which also illustrates the vibration in the prior art E-block 10P and the transducer assemblies 12P with force applied by an actuator motor (not shown). The prior art E-block 10P in FIGS. 1A and 1B includes four actuator arms 14P and six transducer assemblies 12P. The upper most and lower most actuator arms 14P are depopulated while the middle two actuator arms 14P are populated. As a result of the asymmetrical design, the actuator arms 14P and the transducer assemblies 12P each react differently to force applied by the actuator motor and to shock loads to the disk drive.
FIGS. 2A-2C further highlight how the asymmetrical design effect the resonance characteristics of the actuator arms and/or the transducers. For example, FIG. 2A illustrates a computer simulation of the off track motion for each data transducer 16P after force applied by the actuator motor for the E-block illustrated in FIGS. 1A and 1B. FIG. 2B illustrates a computer simulation of the G""s to unload as a function of shock duration for the E-block illustrated in FIGS. 1A and 1B. Stated another way, FIG. 2B illustrates the G""s required to lift the transducer away from the surface of the storage disk for a given shock duration. In FIG. 2B, the curve designated 18P illustrates the movement of the transducer on the depopulated actuator arm while the curves designed 20P each illustrate movement of the transducer for a populated actuator arm. FIG. 2C illustrates the amount of arm deflection for the actuator arms 14P of the E-block 10P as a function of shock duration for the E-block illustrated in FIGS. 1A and 1B. More specifically, in FIG. 2C, curve designated 22P represents the movement of the actuator arm which does not include any transducer assemblies, curve designated 24P represents the movement of the actuator arm with a single transducer assembly, and curve designated 26P represents the movement of the actuator arm having two transducer assemblies attached to the actuator arm.
One attempt to eliminate the effect of the depopulated actuator arms includes attaching a transducer assembly to each side of each actuator arm so that each arm is populated and adding an additional storage disk to the disk drive. However, the two additional transducer assemblies and the additional storage disk increase the cost for the disk drive and take up valuable space in the disk drive. Alternately, to maintain symmetry of the E-block, a three arm E-block with six transducers could be used in place of the four arm E-block. With this design, one extra disk would be required and two surfaces, the outermost surface on the outermost disks, would not be utilized.
Another attempt to minimize off track vibration and head slap includes cantilevering a mass in the form of a dummy swage plate from each depopulated actuator arm. The dummy swage plate can be effective in adding the additional mass to the system. However, the dummy swage plate increases the inertia of the E-block. This results in increased data seek times for the disk drive because the actuator motor is not able to move the E-block as quickly. Further, the dummy swage plate typically has different dynamic behavior and stiffness since it is not practical to make one the full transducer assembly length. Typically, short, simple shaped cantilever beams or swage bases are used. Additionally, the dummy swage plate is somewhat difficult to properly position and attach to the depopulated actuator arm. This adds extra components to the disk drive and increases the manufacturing cost of the disk drive.
Yet another attempt to minimize vibration effecting head slap includes using resilient mounts to secure the disk drive. The resilient mounts flex to attenuate shock and reduce head slap. Unfortunately, the resilient mounts also reduce disk drive performance during a data seek request.
In light of the above, it is an object of the present invention to provide a stable E-block having one or more depopulated actuator arms for a disk drive and method for making the same. Another object of the present invention is to provide an E-block having improved vibration and resonance characteristics, which does not degradate the performance of the disk drive. Still another object of the present invention is to provide an E-block which minimizes head slap and reduces drive fragility to shipping, handling, and installation. Yet another object of the present invention is to provide an E-block which can be adapted to be used with disk drives having an alternate number of storage disks. Still another object of the present invention is to provide an E-block having one or more depopulated actuator arms which is relatively easy and inexpensive to manufacture.
The present invention is directed to an E-block and a method for manufacturing an E-block for a disk drive which satisfies these objectives. The E-block includes an actuator hub and a depopulated actuator arm secured to the actuator hub. The depopulated actuator arm retains less than two transducer assemblies. Uniquely, the depopulated actuator arm includes a first weighted segment integrally formed into the depopulated actuator arm. The first weighted segment is sized, shaped and located to improve the resonance characteristics of the depopulated actuator arm.
The improved resonance characteristics reduce the amount of vibration in the E-block and the transducer assemblies, thereby decreasing off-track motion, minimizing head slap, and increasing the accuracy of the disk drive. Moreover, because the weighted segment is an integral part of the actuator arm and does not cantilever away from the actuator arm, the performance impact to the actuator motor is minimized and the cost for manufacturing the E-block is not increased.
In one embodiment, the depopulated actuator arm is a single head actuator arm which retains a single transducer assembly. The single head actuator arm includes a coupled side and an opposed uncoupled side. The single head actuator arm secures one transducer assembly to the coupled side, near one storage disk. In this embodiment, the weighted segment is preferably sized, shaped and located to counterbalance the single transducer assembly.
In another embodiment, the depopulated actuator arm is a no head actuator arm which retains no transducer assemblies. The no head actuator arm including a pair of spaced apart uncoupled sides and a pair of spaced apart weighted segments. Each weighted segment is integrally formed into the actuator arm and is sized, shaped and positioned to improve the resonance characteristics of the no head actuator arm.
Depending upon the design of the disk drive, the E-block can include one or more single head actuator arms, one or more no head actuator arms and one or more double head actuator arms. As provided in detail below, this feature, for example, allows the same E-block design to be alternately manufactured for disk drives having different numbers of storage disks.
The present invention is also a method for manufacturing an E-block for a disk drive. The method includes the steps of forming an E-block having an actuator hub and a depopulated actuator arm secured to the actuator hub. The depopulated actuator arm includes an uncoupled side and a weighted segment integrally formed into the depopulated actuator arm. The weighted segment is sized, shaped and located to improve the resonance characteristics of the depopulated actuator arm.
Additionally, the arm thickness of each depopulated actuator arm is less than the arm thickness of each double head actuator arm. This causes the lateral stiffness of each depopulated actuator arm to be less than the lateral stiffness of each double head actuator arm. The combination of the weighted segment and reduced lateral stiffness allows each depopulation actuator arm to have approximately the same resonance characteristics as each double head actuator arm.
Importantly, the integrally formed weighted segment and reduced lateral stiffness improves the resonance characteristics of the E-block without significantly increasing the cost of manufacturing or degrading the performance of the disk drive. With the design provided herein, the depopulated actuator arms and the double head actuator arms have substantially similar resonance characteristics. This allows the disk drive manufacturer to better design and tune the disk drive to minimize head slap and off-track motion. Further, the disk drive can be better tuned to improve the fragility of the disk drive to shock loads during shipping and handling.